Maternal smoking in successive pregnancies and recurrence of low birthweight: the 2004 Pelotas birth cohort study, Brazil.

To evaluate the frequency of maternal smoking in successive pregnancies and its association with repetition of low birthweight, a study was conducted of a subsample of mothers from the 2004 Pelotas Birth Cohort in Brazil. Only women with previous histories of low birthweight newborns were included. Women with ≥ 2 previous births were eligible only if at least one of the two births immediately preceding the 2004 birth had low birthweight. From 4,458 births, 565 were included in this study. Frequency of smoking was 32.4%. Considering past pregnancies, 67.1% of mothers never smoked, 21.4% smoked during all pregnancies, 6.5% were ex-smokers, and 5% smoked only during the current pregnancy. In the adjusted analyses, when compared to mothers who never smoked, those who smoked during all pregnancies had 2.5 times greater probability of low birthweight recurrence in 2004 (PR = 2.5; 95%CI: 1.32-4.80). Smoking persistence is an important factor for the recurrence of low birthweight in successive pregnancies.